1. Field of the Invention
The present invention relates in general to the field of information handling system peripheral testing, and more particularly to a system and method for information handling system peripheral EMC test.
2. Description of the Related Art
As the value and use of information continues to increase, individuals and businesses seek additional ways to process and store information. One option available to users is information handling systems. An information handling system generally processes, compiles, stores, and/or communicates information or data for business, personal, or other purposes thereby allowing users to take advantage of the value of the information. Because technology and information handling needs and requirements vary between different users or applications, information handling systems may also vary regarding what information is handled, how the information is handled, how much information is processed, stored, or communicated, and how quickly and efficiently the information may be processed, stored, or communicated. The variations in information handling systems allow for information handling systems to be general or configured for a specific user or specific use such as financial transaction processing, airline reservations, enterprise data storage, or global communications. In addition, information handling systems may include a variety of hardware and software components that may be configured to process, store, and communicate information and may include one or more computer systems, data storage systems, and networking systems.
Information handling systems are growing consistently more powerful due, in part, to improvements in the components used to build information handling systems. For example, central processing units (CPUs) have seen greater numbers of features packed into a given area and have seen increases in operating speeds. Hard disk drives are built to rotate at greater speeds and retrieve and store information at greater rates. Random access memory (RAM) stores more information in a given area and stores and retrieves information with increased speed, such as with double data rate protocols. Information is communicated between components with serial links that have high frequency clock signals. Serial links have also substantially improved and simplified peripheral interfaces with information handling systems through external cables, such as interfaces with displays, mice, keyboards, printers and mass storage devices. As an example, the Universal Serial Bus (USB) is widely accepted through the industry to interface a wide variety of external peripherals with information handling systems.
One difficulty with the improved performance of information handling system components is that the greater operating speeds tend to produce greater amounts of electromagnetic interference (EMI). For example, current signaling schemes associated with high speed differential links operate at 3 GB/s for SAS and 4 GB/s for FC with future signaling schemes projected to operate at 10/GB/s or higher. Information handling system manufacturers are required by regulatory agencies to meet defined standards that limit the amount of EMI from a system. To meet regulatory standards, manufacturers design component layout and chassis shielding so that worst case operating conditions will not exceed defined EMI limits. The systems are typically tested by reading EMI with a spectrum analyzer located outside of the chassis. However, EMI measurements sometimes vary from predicted levels when information handling systems use peripherals interfaced through an external cable due to a common-mode component. The electromagnetic compatibility (EMC) of an information handling system with various peripherals is often difficult to predict since the EMC measurement sometimes exceeds the sum of the expected individual EMIs. For example, an information handling system interfaced by a USB cable with an external hard drive might exceed EMI requirements even though the information handling system and hard drive meet individual EMI requirements. Isolating the source of the excess EMI, such as hard drive operations versus the system data traffic or crosstalk onto external signals, is difficult.